Polishing apparatus

ABSTRACT

A polishing apparatus according to the present invention has a polishing surface ( 101 ), a top ring ( 1 ) for holding a semiconductor wafer (W), and a top ring shaft ( 11 ) for pressing the top ring ( 1 ) against the polishing surface ( 101 ). The top ring ( 1 ) has a retainer ring ( 3 ) for holding a peripheral portion of the semiconductor wafer (W), a housing ( 2 ) substantially in a form of a disk which is connected to the top ring shaft ( 11 ), a sliding contact joint ( 4, 5, 6, 2   b ) interconnecting the retainer ring ( 3 ) and the housing ( 2 ) in a state such that the retainer ring ( 3 ) and the housing ( 2 ) are brought into sliding contact with each other.

TECHNICAL FIELD

The present invention relates to a polishing apparatus, and morearticularly to a polishing apparatus for polishing a workpiece to bepolished, such as a semiconductor wafer, by holding the workpiece andpressing the workpiece against a polishing surface.

BACKGROUND ART

In recent years, semiconductor devices have become more integrated, andstructures of semiconductor elements have become more complicated.Further, the number of layers in multilayer interconnections used for alogical system has been increased. Accordingly, irregularities on asurface of a semiconductor device are increased, so that step heights onthe surface of the semiconductor device tend to be large. This isbecause, in a manufacturing process of a semiconductor device, a thinfilm is formed on a semiconductor device, then micromachining processes,such as patterning or forming holes, are performed on the semiconductordevice, and these processes are repeated to form subsequent thin filmson the semiconductor device.

When the number of irregularities is increased on a surface of asemiconductor device, the following problems arise. When a thin film isformed on a semiconductor device, the thickness of the film formed atportions having a step becomes small. Further, an open circuit may becaused by disconnection, or a short circuit may be caused byinsufficient insulation between interconnection layers. As a result,good products cannot be obtained, and the yield tends to be lowered.Further, even if a semiconductor device initially works normally,reliability of the semiconductor device is lowered after a long-termuse. At the time of exposure in a lithography process, if theirradiation surface has irregularities, then a lens unit in an exposuresystem is locally unfocused. Therefore, if the irregularities on thesurface of the semiconductor device are increased, then it becomesproblematically difficult to form a fine pattern itself on thesemiconductor device.

Thus, in a manufacturing process of a semiconductor device, itincreasingly becomes important to planarize a surface of thesemiconductor device. One of the most important planarizing technologiesis chemical mechanical polishing (CMP). In a chemical mechanicalpolishing, while a polishing liquid containing abrasive particles suchas silica (SiO₂) therein is supplied onto a polishing surface such as apolishing pad, a substrate such as a semiconductor wafer is brought intosliding contact with the polishing surface, so that the substrate ispolished.

This type of polishing apparatus includes a polishing table having apolishing surface formed by a polishing pad and a top ring for holding asemiconductor wafer. When a semiconductor wafer is polished with such apolishing apparatus, the semiconductor wafer is held and pressed againstthe polishing table under a predetermined pressure by the top ring. Atthat time, the polishing table and the top ring are moved relative toeach other to bring the semiconductor wafer into sliding contact withthe polishing surface, so that the surface of the semiconductor wafer ispolished to a flat mirror finish.

The polishing pad is so elastic that pressing forces applied to aperipheral edge portion of the semiconductor wafer tend to benon-uniform. Accordingly, the semiconductor wafer may excessively bepolished only at the peripheral edge portion to thus cause edgerounding. In order to prevent such edge rounding, as shown in FIG. 1,there has been employed a top ring having a structure for holding a sideedge portion of a semiconductor wafer W by a retainer ring 600 andpressing a polishing surface 610 located outside of a peripheral edgeportion of the semiconductor wafer W by the retainer ring 600. In thistype of top ring, as shown in FIG. 1, the retainer ring 600 is fixed toa peripheral portion of a disk-like housing (flange portion) 620 andpressed against the polishing surface 610 under a pressing force appliedby a top ring shaft 630, which is connected to a central portion of thehousing 620.

In the aforementioned conventional top ring, since the retainer ring 600and the housing 620 are rigidly connected to each other, as shown inFIG. 1, a bending moment M₀ is produced in the housing 620 and theretainer ring 600 due to a pressing force of the top ring shaft 630which is applied to a central portion of the housing 620. Accordingly,the retainer ring 600 is inclined by deformation due to the bendingmoment M₀. When the retainer ring 600 is thus inclined, the surfacepressure is not constant on the lower surface of the retainer ring 600.Therefore, the retainer ring 600 is partially worn. For this reason,highly accurate polishing cannot be achieved.

Specifically, in order to improve a polishing performance, a portion forpressing a workpiece W to be polished tends to have a complicatedstructure. Since the top ring has a complicated pressing mechanism, aportion at which the retainer ring 600 is attached to the housing 620 isseparated from an outer peripheral edge of the workpiece W in acircumferential direction so as to form an overhanging portion in viewof structural mechanics. A bending moment M₀ produced by the overhangingdeforms the retainer ring 600 as shown in FIG. 1 so that the surfacepressure of the retainer ring 600 to the polishing surface 610 becomesnon-uniform. If the retainer ring 600 is partially worn according toprogress of polishing time, then a polishing profile varies so as toexert an adverse influence on polishing stability.

Thus, in the aforementioned polishing apparatus, the retainer ring 600for holding a peripheral portion of the workpiece W is required to havea function to uniformly press the polishing surface 610 of the polishingtable in addition to a function to hold the workpiece W.

DISCLOSURE OF INVENTION

The present invention has been made in view of the above drawbacks. Itis, therefore, a first object of the present invention to provide apolishing apparatus which can prevent or reduce partial wear of aretainer ring during polishing so as to conduct highly accuratepolishing.

A second object of the present invention is to provide a polishingapparatus which can reduce cost for expendables and environment loads,enhance reliability, and shorten a period of time required to conductdummy polishing after a new retainer ring is attached to a housing.

A third object of the present invention is to provide a retainer ringwhich allows dummy polishing, which has been required to be performed ona polishing apparatus, to be performed on a separate dedicated apparatusor machine tool.

In order to attain the first object, according to a first aspect of thepresent invention, there is provided a polishing apparatus having apolishing surface, a top ring for holding a workpiece to be polished,and a top ring shaft for pressing the top ring against the polishingsurface. The top ring has a retainer ring for holding a peripheral edgeportion of the workpiece, a housing substantially in a form of a diskwhich is connected to the top ring shaft, and a sliding contact jointinterconnecting the retainer ring and the housing in a state such thatthe retainer ring and the housing are brought into sliding contact witheach other.

With such an arrangement, when the top ring is pressed against thepolishing surface, the retainer ring and the housing are brought intosliding contact with each other. Accordingly, even if the top ring shaftapplies a load to a central portion of the housing, only a verticalcomponent of the load is transmitted to the retainer ring while nobending moment is applied to the retainer ring because the housing andthe retainer ring slide with respect to each other. As a result, theretainer ring is not tilted due to a bending moment. Thus, it ispossible to prevent partial wear from being caused on a lower surface ofthe retainer ring.

The sliding contact joint may comprise a free joint, preferably a balljoint, to bring the retainer ring and the housing into sliding contactwith each other.

According to a second aspect of the present invention, there is provideda polishing apparatus having a polishing surface, a top ring for holdinga workpiece to be polished, and a top ring shaft for pressing the topring against the polishing surface. The top ring has a retainer ring forholding a peripheral edge portion of the workpiece, a housingsubstantially in a form of a disk which is connected to the top ringshaft, and a joint interconnecting the retainer ring and the housing.The joint has a sufficient high rigidity in horizontal and verticaldirections and a low flexural rigidity.

Thus, since the rigidity of the joint is increased in the horizontal andvertical directions, a load can reliably be transmitted from the topring shaft to the retainer ring. Further, since the flexural rigidity ofthe joint is lowered, a bending moment due to a load applied to acentral portion of the housing can be absorbed by the joint to reduce abending moment applied to the retainer ring. Accordingly, it is possibleto prevent inclination of the retainer ring and reduce partial wear ofthe lower surface of the retainer ring.

It is desirable that the joint is disposed outside of a center of aradial width of the retainer ring. When the joint is disposed outside ofthe center of the radial width of the retainer ring, a load of the topring shaft is applied to a portion located outside of the center of theradial width of the retainer ring. Accordingly, a bending moment isproduced with respect to the center of the width of the retainer ring.This bending moment cancels a bending moment produced by a load appliedto the central portion of the housing. Thus, a bending moment applied tothe retainer ring 3 can further be reduced. Accordingly, it is possibleto reduce partial wear of the lower surface of the retainer ring moreeffectively. The joint may have a cross-section constricted at avertically central portion thereof.

According to a third aspect of the present invention, there is provideda polishing apparatus having a polishing surface, a top ring for holdinga workpiece to be polished, and a top ring shaft for pressing the topring against the polishing surface. The top ring has a retainer ring forholding a peripheral edge portion of the workpiece and a housingsubstantially in a form of a disk which is connected to the top ringshaft. A rigidity of the housing is increased so that an inclination ofa lower surface of the retainer ring is reduced with respect to thepolishing surface when the top ring is pressed against the polishingsurface.

For example, the housing may be made of a material having high strengthand rigidity, such as metal or ceramics, and thickened so as to have ahigh rigidity. Thus, when the housing has a high rigidity, a bendingmoment becomes unlikely to be applied to the retainer ring even if aload is applied to the central portion of the housing by the top ringshaft. Accordingly, it is possible to prevent partial wear of theretainer ring.

In order to attain the second object, according to a fourth aspect ofthe present invention, there is provided a polishing apparatus forpolishing a workpiece to be polished, such as a semiconductor wafer, toa flat mirror finish. The polishing apparatus has a polishing surfaceand a top ring for holding a workpiece to be polished. The top ring hasa retainer ring for holding a peripheral edge portion of the workpiece.The retainer ring has a first ring member made of resin, a second ringmember made of metal or ceramic, and a fastening tool for fastening thefirst ring member and the second ring member in a manner such that thefirst ring member and the second ring member can be detached as twolayers in a vertical direction.

With such an arrangement, it is possible to enhance the reliability offastening the first ring member and the second ring member. Further, theretainer ring can be regenerated merely by replacement of a worn firstring member. Accordingly, it is possible to reduce cost for expendables.Furthermore, when the retainer ring is attached to a lower surface of aperipheral portion of the housing by a detachable fastening tool, aclamp stress is received by the second ring member such as metal orceramics, which has a high rigidity. Thus, the retainer ring isprevented from being deformed. Therefore, it is possible to shorten aperiod of time, i.e., downtime, required for a dummy polishing process.

It is desirable that the first ring member is brought into contact withthe polishing surface. It is also desirable that the first ring memberincludes particles serving as abrasive particles when the first ringmember is scraped. In this case, particles scraped from the first ringmember of the retainer ring serve as abrasive particles. Thus, abrasiveparticles are supplied from the retainer ring by supplying, e.g., purewater to the polishing surface.

It is desirable that the retainer ring further includes an engagementportion to fit the first ring member and the second ring member intoeach other. With such an arrangement, it is possible to facilitateassembling the retainer ring and further enhance the reliability offastening the first ring member and the second ring member.

The retainer ring is preferably configured such that the retainer ringcan be regenerated only by replacement of the first ring member. Sincethe retainer ring can be regenerated merely by replacement of the firstring member, it is possible to reduce cost for expendables andenvironment loads.

It is desirable that the fastening tool comprises a bolt. When a bolt isused as the fastening tool, it is possible to facilitate fastening,assembling, and disassembling the first ring member and the second ringmember.

In order to attain the third object, according to a fifth aspect of thepresent invention, there is provided a retainer ring for holding aperipheral edge portion of a workpiece to be polished, which is held ona substrate holding surface of a top ring. The retainer ring has a firstring member made of resin, a second ring member made of metal orceramic, and a fastening tool for fastening the first ring member andthe second ring member in a manner such that the first ring member andthe second ring member can be detached as two layers in a verticaldirection. The first ring member is polished to have flatness.

Thus, the first ring member and the second ring member can be fastenedby a detachable fastening tool to form a retainer ring having atwo-layer structure in the vertical direction. Then, the first ringmember can be polished so as to have flatness. Accordingly, it is notnecessary to conduct dummy polishing on the polishing apparatus whichhas heretofore been required.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view showing a conventional top ring;

FIG. 2 is a schematic view showing an entire arrangement of a polishingapparatus according to a first embodiment of the present invention;

FIG. 3 is a vertical cross-sectional view of a top ring in the polishingapparatus shown in FIG. 2 on a cutting plane;

FIG. 4 is a vertical cross-sectional view of the top ring in thepolishing apparatus shown in FIG. 2 on another cutting plane;

FIG. 5 is a plan view showing a sliding contact joint (housing) of thetop ring shown in FIG. 3;

FIG. 6 is a vertical cross-sectional view showing a variation of the topring shown in FIG. 3;

FIG. 7 is a vertical cross-sectional view showing a top ring accordingto a second embodiment of the present invention;

FIG. 8 is a schematic view showing the top ring shown in FIG. 7;

FIG. 9 is a vertical cross-sectional view showing a top ring accordingto a third embodiment of the present invention;

FIG. 10A is a vertical cross-sectional view showing an attachmentportion of a retainer ring of the top ring shown in FIG. 9;

FIG. 10B is a view showing a surface pressure distribution in theretainer ring shown in FIG. 10A;

FIG. 11 is a plan view showing an example of an arrangement of bolts inthe retainer ring shown in FIG. 9;

FIG. 12 is a plan view showing another example of an arrangement ofbolts in the retainer ring shown in FIG. 9;

FIG. 13A is a vertical cross-sectional view showing an attachmentportion of a conventional retainer ring;

FIG. 13B is a view showing a surface pressure distribution in theretainer ring shown in FIG. 13A;

FIG. 14 is a vertical cross-sectional view showing a top ring accordingto a fourth embodiment of the present invention;

FIG. 15 is a cross-sectional view showing a variation of the top ringshown in FIG. 14;

FIG. 16 is a cross-sectional view showing a variation of the top ringshown in FIG. 14;

FIG. 17A is an enlarged cross-sectional view of a main portion of a topring according to a fifth embodiment of the present invention;

FIG. 17B is an enlarged cross-sectional view of a main portion of a topring according to a sixth embodiment of the present invention;

FIGS. 18A and 18B are enlarged cross-sectional views showing variationsof the retainer ring shown in FIG. 14;

FIG. 19 is an enlarged cross-sectional view showing a variation of theretainer ring shown in FIG. 14; and

FIG. 20 is a graph showing a surface pressure distribution along aradial direction of a lower surface of the retainer ring shown in FIG.17B.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of a polishing apparatus according to the present inventionwill be described below with reference to FIGS. 2 through 20. In FIGS. 2through 20, like or corresponding parts are denoted by like orcorresponding reference numerals and will not be described belowrepetitively.

FIG. 2 is a schematic view showing an entire arrangement of a polishingapparatus according to a first embodiment of the present invention. Asshown in FIG. 2, a polishing table 100 having a polishing pad 101attached to an upper surface thereof is provided below a top ring 1.Further, a polishing liquid supply nozzle 102 is provided above thepolishing table 100. A polishing liquid Q is supplied from the polishingliquid supply nozzle 102 to the polishing pad 101 on the polishing table100.

Various kinds of polishing pads are available on the market. Forexample, some of these are SUBA800, IC-1000, and IC-1000/SUBA400(two-layer cloth) manufactured by Rodel Inc., and Surfin xxx-5 andSurfin 000 manufactured by Fujimi Inc. SUBA800, Surfin xxx-5, and Surfin000 are non-woven fabrics bonded by urethane resin, and IC-1000 is madeof hard rigid foam polyurethane (single layer). Foam polyurethane isporous and has a large number of fine recesses or holes formed in itssurface.

The top ring 1 is connected to a top ring shaft 11 via a universal joint10, and the top ring shaft 11 is coupled to a top ring air cylinder 111fixed to a top ring head 110. The top ring 1 has a housing 2 (flangeportion) substantially in the form of a disk, which is coupled to alower end of the top ring shaft 11, and a retainer ring 3 disposed at aperipheral portion of the housing 2.

The top ring air cylinder 111 is connected to a pressure adjustment unit120 via a regulator R1. The pressure adjustment unit 120 serves toadjust a pressure by supply of a pressurized fluid such as pressurizedair from a compressed air source or by evacuation with pump or the likeThe air pressure of the pressurized air to be supplied to the top ringair cylinder 111 is adjusted via the regulator R1 by the pressureadjustment unit 120. The top ring air cylinder 111 moves the top ringshaft 11 vertically to raise and lower the whole top ring 1 and pressthe retainer ring 3 attached to the housing 2 against the polishingtable 100 under a predetermined pressing force.

The top ring shaft 11 is coupled to a rotary sleeve 112 by a key (notshown). The rotary sleeve 112 has a timing pulley 113 disposed at aperipheral portion thereof A top ring motor 114 is fixed to the top ringhead 110. The timing pulley 113 is connected to a timing pulley 116mounted on the top ring motor 114 via a timing belt 115. Accordingly,when the top ring motor 114 is energized for rotation, the rotary sleeve112 and the top ring shaft 11 are rotated in unison with each other viathe timing pulley 116, the timing belt 115, and the timing pulley 113 tothereby rotate the top ring 1. The top ring head 110 is supported on atop ring head shaft 117 rotatably supported on a frame (not shown).

The top ring 1 will be described in greater details. FIG. 3 is avertical cross-sectional view of the top ring 1 shown in FIG. 2 on acutting plane, FIG. 4 is a vertical cross-sectional view of the top ring1 shown in FIG. 2 on another cutting plane, and FIG. 5 is a plan viewshowing the housing 2 of the top ring 1 shown in FIG. 3.

As shown in FIGS. 3 and 4, the retainer ring 3 has an upper member 3 asubstantially in the form of a cylinder and a lower member 3 bsubstantially in the form of a cylinder. The lower member 3 b has alower portion projecting inward. As shown in FIGS. 3 and 5, ball joints4 are provided as free joints to bring the retainer ring 3 and thehousing 2 into sliding contact with each other at a plurality oflocations in a circumferential direction of the retainer ring 3 on anupper portion of the upper member 3 a of the retainer ring 3. The balljoints 4 are interposed between hemispherical recesses 2 a formed in alower surface of the housing 2 and hemispherical recesses 3 c formed inan upper surface of the upper member 3 a of the retainer ring 3.

As shown in FIGS. 4 and 5, connection bolts 5 are provided on an upperportion of the upper member 3 a of the retainer ring 3 at a plurality oflocations in the circumferential direction. The housing 2 has springreceivers 2 b corresponding to the connection bolts 5. Coil springs 6are interposed between the connection bolts 5 and the spring receivers 2b. Thus, the ball joints 4, the connection bolts 5, the spring receivers2 b, and the coil springs 6 jointly form sliding contact joints tointerconnect the retainer ring 3 and the housing 2 in a state such thatthe retainer ring 3 and the housing 2 are brought into sliding contactwith each other. In the present embodiment, the retainer ring 3 and thehousing 2 are brought into sliding contact with each other by the balljoints 4. However, any means can be used as long as it brings theretainer ring 3 and the housing 2 into sliding contact with each other.

As described above, the top ring shaft 11 is disposed above a centralportion of the housing 2, and the housing 2 is coupled to the top ringshaft 11 by the universal joint 10. The universal joint 10 has aspherical bearing mechanism by which the housing 2 and the top ringshaft 11 are tiltable with respect to each other, and a rotationtransmitting mechanism for transmitting rotation of the top ring shaft11 to the housing 2. These mechanisms transmit a pressing force and arotating force from the top ring shaft 11 to the housing 2 whileallowing the housing 2 and the top ring shaft 11 to be tilted withrespect to each other.

The spherical bearing mechanism includes a hemispherical recess 11 adefined centrally in a lower surface of the top ring shaft 11, ahemispherical recess 2 c defined centrally in an upper surface of thehousing 2, and a bearing ball 12 made of a highly hard material such asceramics and interposed between the recesses 11 a and 2 c. As shown inFIG. 3, connection bolts 7 are mounted near the top ring shaft 11 of thehousing 2. Coil springs 8 are interposed between the connection bolts 7and spring receivers 11 b provided in the top ring shaft 11. With such astructure, the housing 2 is held so as to be tiltable with respect tothe top ring shaft 11.

Meanwhile, the rotation transmitting mechanism includes engagement pins9 fixed to the housing 2 near the top ring shaft 11 and engagement holes11 c formed in the top ring shaft 11. Even if the housing 2 is tiltedwith respect to the top ring shaft 11, the engagement pins 9 remain inengagement with the engagement holes 11 c while contact points aredisplaced because the engagement pins 9 are vertically movable throughthe engagement holes 11 c. Thus, the rotation transmitting mechanismreliably transmits rotational torque of the top ring shaft 11 to thehousing 2.

The housing 2 and the retainer ring 3 have a space defined therein,which accommodates therein an elastic pad 20 brought into contact withthe semiconductor wafer W held by the top ring 1, an annular holder ring21, and a chucking plate 22 substantially in the form of a disk forsupporting the elastic pad 20. The elastic pad 20 has a radially outeredge clamped between the holder ring 21 and the chucking plate 22 fixedto a lower end of the holder ring 21 and covers a lower surface of thechucking plate 22. Thus, a pressure chamber 30 is defined between theelastic pad 20 and the chucking plate 22. The elastic pad 20 is made ofa highly strong and durable rubber material such as ethylene propylenerubber (EPDM), polyurethane rubber, or silicone rubber.

An opening 22 a is formed at a central portion of the chucking plate 22.A fluid passage 40 comprising tubes and connectors communicate with theopening 22 a, which is connected to the pressure adjustment unit 120 viaa regulator R2 provided on the fluid passage 40. Specifically, thepressure chamber 30 between the elastic pad 20 and the chucking plate 22is connected to the pressure adjustment unit 120 via the regulator R2provided on the fluid passage 40.

A pressurizing sheet 23 comprising an elastic membrane extends betweenthe holder ring 21 and the housing 2. The pressurizing sheet 23 has oneend clamped by a pressurizing sheet support 2d mounted to a lowersurface of the housing 2 and another end clamped between an upper endportion 21 a and a stopper portion 21 b of the holder ring 21. Thehousing 2, the chucking plate 22, the holder ring 21, and thepressurizing sheet 23 jointly define a pressure chamber 31 in thehousing 2. As shown in FIG. 3, a fluid passage 41 comprising tubes andconnectors communicates with the pressure chamber 31, which is connectedto the pressure adjustment unit 120 via a regulator R3 provided on thefluid passage 41. The pressurizing sheet 23 is made of a highly strongand durable rubber material such as ethylene propylene rubber (EPDM),polyurethane rubber, or silicone rubber.

The pressure chamber 30 between the chucking plate 22 and the elasticpad 20 and the pressure chamber 31 above the chucking plate 22 arerespectively supplied with pressurized fluids such as pressurized air,released to an atmospheric pressure, or evacuated, via the fluidpassages 40 and 41 connected to the pressure chambers 30 and 31.Specifically, as shown in FIG. 2, the regulators R2 and R3 provided onthe fluid passages 40 and 41 of the pressure chambers 30 and 31 canrespectively regulate pressures of the pressurized fluids to be suppliedto the respective pressure chambers. Thus, it is possible toindependently control the pressures in the pressure chambers 30 and 31or independently introduce atmospheric air or vacuum into the pressurechambers 30 and 31.

Further, the chucking plate 22 has inner suction portions 24 and outersuction portions 25 projecting downward outside of the opening 22 a. Theinner suction portions 24 have communication holes 24 a communicatingwith a fluid passage 42, which comprises tubes and connectors. The innersuction portions 40 are connected to the pressure adjustment unit 120via a regulator R4 provided on the fluid passage 42. Similarly, theouter suction portions 25 have communication holes 25 a communicatingwith a fluid passage 43, which comprises tubes and connectors. The outersuction portions 25 are connected to the pressure adjustment unit 120via a regulator R5 provided on the fluid passage 43. Negative pressurescan be developed at opening ends of the communication holes 24 a and 25a of the suction portions 24 and 25 by the pressure adjustment unit 120,thereby attracting a semiconductor wafer W to the suction portions 24and 25. The suction portions 24 and 25 have elastic sheets, such as thinrubber sheets, attached to their lower ends, to thereby softly attractand hold the semiconductor wafer W.

As shown in FIG. 3, a cleaning liquid passage 26 is formed in the uppermember 3 a of the retainer ring 3. The cleaning liquid passage 26communicates with a slight gap between an outer circumferential surfaceof the elastic pad 20 and the lower member 3 b of the retainer ring 3. Acleaning liquid (pure water) is supplied to the gap through the cleaningliquid passage 26.

In the polishing apparatus thus constructed, when a semiconductor waferW to be delivered, the entire top ring 1 is moved to a transferringlocation of the semiconductor wafer. Then, the communication holes 24 aand 25 a of the suction portions 24 and 25 are connected to the pressureadjustment unit 120 via the fluid passages 42 and 43. The semiconductorwafer W is attracted under vacuum to the lower ends of the suctionportions 24 and 25 by suction effect of the communication holes 24 a and25 a. While the semiconductor wafer W is attracted to the suctionportions, the entire top ring 1 is moved to a position above thepolishing table 100 having the polishing surface (polishing pad 101)thereon. The outer circumferential edge of the semiconductor wafer W isheld by the retainer ring 3 so that the semiconductor wafer W is notremoved from the top ring 1.

For polishing, the attraction of the semiconductor wafer W by thesuction portions 24 and 25 is released, and the semiconductor wafer W isheld on the lower surface of the top ring 1. Simultaneously, the topring air cylinder 111 connected to the top ring shaft 11 is actuated topress the retainer ring 3 fixed to the lower end of the top ring 1against the polishing surface on the polishing table 100 under apredetermined pressing force. In such a state, a pressurized fluidhaving a predetermined pressure is supplied to the pressure chamber 30to thereby press the semiconductor wafer W against the polishing surfaceon the polishing table 100. The polishing liquid supply nozzle 102supplies a polishing liquid Q onto the polishing pad 101 in advance, sothat the polishing liquid Q is held on the polishing pad 101. Thus, thesemiconductor wafer W is polished with the polishing liquid Q beingpresent between the (lower) surface, to be polished, of thesemiconductor wafer W and the polishing pad 101.

When a pressurized fluid is supplied to the pressure chamber 30, anupward force is applied to the chucking plate 22. Accordingly, in thepresent embodiment, a pressure fluid is supplied to the pressure chamber31 through the fluid passage 41 to prevent the chucking plate 22 frombeing lifted by forces from the pressure chamber 31.

As described above, the pressing force applied by the top ring aircylinder 111 to press the retainer ring 3 against the polishing pad 101and the pressing force applied by the pressurized air supplied to thepressure chamber 30 to press the semiconductor wafer W against thepolishing pad 101 are appropriately adjusted to polish the semiconductorwafer W. When the polishing of the semiconductor wafer W is finished,the semiconductor wafer W is attracted to the lower ends of the suctionportions 24 and 25 under vacuum. At that time, the supply of thepressurized-fluid into the pressure chamber 30 to press thesemiconductor wafer W against the polishing surface is stopped, and thepressure chamber 30 is vented to the atmosphere. Accordingly, the lowerends of the suction portions 24 and 25 are brought into contact with thesemiconductor wafer W. The pressure chamber 31 is vented to theatmosphere or evacuated to develop a negative pressure therein. If thepressure chamber 31 is maintained at a high pressure, then thesemiconductor wafer W is strongly pressed against the polishing surfaceonly in areas brought into contact with the suction portions 40.

After attraction of the semiconductor wafer W, the entire top ring 1 ismoved to a transferring position of the semiconductor wafer W, and thena fluid (e.g., compressed air or a mixture of nitrogen and pure water)is ejected to the semiconductor wafer W via the communication holes 24 aand 25 a of the suction portions 24 and 25 to release the semiconductorwafer W from the top ring 1.

As described above, in the present embodiment, when the top ring 1 ispressed against the polishing surface, the retainer ring 3 and thehousing 2 are brought into sliding contact with each other by the balljoints 4. Accordingly, even if the top ring shaft 11 applies a load tothe central portion of the housing 2, only a vertical component of theload is transmitted to the retainer ring 3 while no bending moment isapplied to the retainer ring 3 because the housing 2 and the retainerring 3 slide with respect to each other. As a result, the retainer ring3 is not tilted due to a bending moment. Thus, it is possible to preventpartial wear from being caused on a lower surface of the retainer ring3.

Here, the aforementioned bending moment can also be prevented from beingapplied to the retainer ring 3 by enhancing a rigidity of the housing 2.For example, the housing 2 may be made of a material having highstrength and rigidity, such as metal or ceramics, and thickened so as tohave a high rigidity. Thus, an inclination of the lower surface of theretainer ring 3 with respect to the polishing pad 101 is reduced whenthe top ring 1 is pressed against the polishing pad 101. When thehousing 2 has a high rigidity, a bending moment becomes unlikely to beapplied to the retainer ring 3 even if a load is applied to the centralportion of the housing 2 by the top ring shaft 11. Accordingly, it ispossible to prevent partial wear of the retainer ring 3.

In the present embodiment, the aforementioned sliding contact joints caneliminate bending moments applied to the retainer ring 3. Accordingly,it is not necessary to enhance the rigidity of the housing 2 to preventgeneration of bending moments. Thus, as shown in FIG. 6, the housing 2can be thinned so as to be lightweight, thereby improving easiness ofmaintenance.

FIG. 7 is a vertical cross-sectional view showing a top ring accordingto a second embodiment of the present invention. As shown in FIG. 7, inthe present embodiment, a joint 50 is provided instead of the slidingcontact joints in the first embodiment. The joint 50 interconnects anupper member 3 a of a retainer ring 3 and a housing 2 and has asufficient high rigidity in horizontal and vertical directions and a lowflexural rigidity. In the present embodiment, in order to have asufficient high rigidity in horizontal and vertical directions and a lowflexural rigidity, the joint 50 has a constricted cross-section suchthat the width of a vertically central portion thereof is smaller thanupper and lower portions thereof. Even with a constricted cross-section,since the joint 50 receives a load in one direction with its perimeter,a sufficient rigidity can be maintained in the horizontal direction. Atthat time, bending moments are received by the respectivecross-sections. As a result, the flexural rigidity becomes lower thanthe rigidity in the horizontal direction.

In the present embodiment, since the rigidity of the joint 50 isincreased in the horizontal and vertical directions, a load can reliablybe transmitted from the top ring shaft 11 to the retainer ring 3.Further, since the flexural rigidity of the joint 50 is lowered, abending moment due to a load applied to the central portion of thehousing 2 can be absorbed by the joint 50 to reduce a bending momentapplied to the retainer ring 3. Accordingly, it is possible to preventinclination of the retainer ring 3 and reduce partial wear of the lowersurface of the retainer ring 3. In the present embodiment, the housing2, the joint 50, and the upper member 3 a of the retainer ring 3 areformed integrally with each other. However, the present invention is notlimited to this example.

As described above, the joint 50 having a low flexural rigidity canreduce a bending moment applied to the retainer ring 3. As shown in FIG.7, when the joint 50 is disposed outside of the center of the radialwidth of the retainer ring 3, it is possible to further reduce a bendingmoment applied to the retainer ring 3. Specifically, when the joint 50is disposed outside of the center of the radial width of the retainerring 3, a load of the top ring shaft 11 is applied to a portion locatedoutside of the center of the radial width of the retainer ring 3 asshown in FIG. 8. Accordingly, a bending moment M₁ is produced withrespect to the center of the width of the retainer ring 3. This bendingmoment M₁ cancels a bending moment M₂ produced by a load applied to thecentral portion of the housing 2. Thus, a bending moment applied to theretainer ring 3 can further be reduced. Accordingly, it is possible toreduce partial wear of the lower surface of the retainer ring 3 moreeffectively.

In the present embodiment, one end of a pressurizing sheet 23 is clampedbetween the upper member 3 a of the retainer ring 3 and a pressurizingsheet support 3 d provided radially inward of the upper member 3 a butmay be fixed to the housing 2 as with the first embodiment.

FIG. 9 is a vertical cross-sectional view showing a top ring 301according to a third embodiment of the present invention. As shown inFIG. 9, the top ring 301 has a housing 302 and a retainer ring 303attached to a lower end of a peripheral edge portion of the housing 302.The housing 302 is made of a material having high strength and rigidity,such as metal or ceramics. The housing 302 has a housing body 302 a inthe form of a cylindrical receptacle and an annular pressurizing sheetsupport 302 b fitted inside of a cylindrical portion of the housing body302 a. The retainer ring 303 is fixed to a lower end of the housing body302 a of the housing 302 by bolts 308.

The top ring shaft 311 is disposed above a central portion of thehousing body 302 a of the housing 302, and the housing 302 is coupled tothe top ring shaft 311 by the universal joint 310. The universal joint310 has a spherical bearing mechanism by which the housing 302 and thetop ring shaft 311 are tiltable with respect to each other, and arotation transmitting mechanism for transmitting rotation of the topring shaft 311 to the housing 302. These mechanisms transmit a pressingforce and a rotating force from the top ring shaft 311 to the housing302 while allowing the housing 302 and the top ring shaft 311 to betilted with respect to each other.

The spherical bearing mechanism includes a hemispherical recess 311adefined centrally in a lower surface of the top ring shaft 311, ahemispherical recess 302 c defined centrally in an upper surface of thehousing body 302 a, and a bearing ball 312 made of a highly hardmaterial such as ceramics and interposed between the recesses 311 a and302 c. Meanwhile, the rotation transmitting mechanism includes drivepins (not shown) fixed to the top ring shaft 311 and driven pins (notshown) fixed to the housing body 302 a. Even if the housing 302 istilted with respect to the top ring shaft 311; the drive pins and thedriven pins remain in engagement with each other while contact pointsare displaced because the drive pin and the driven pin are verticallymovable relative to each other. Thus, the rotation transmittingmechanism reliably transmits rotational torque of the top ring shaft 311to the housing 302.

The housing 302 and the retainer ring 303 attached to the housing 302have a space defined therein, which accommodates therein an elastic pad304 brought into contact with a semiconductor wafer W, to be polished,held by the top ring 301, an annular holder ring 305, annular elasticpad supports 309 and 313 for supporting the elastic pad 304, and achucking plate 306 substantially in the form of a disk for supportingthe elastic pad supports 309 and 313. The elastic pad 304 has a radiallyouter edge clamped between the chucking plate 306 and the elastic padsupports 309 and 313 and covers lower surfaces of the elastic padsupports 309 and 313.

A pressurizing sheet 307 comprising an elastic membrane extends betweenthe holder ring 305 and the housing 302. The pressurizing sheet 307 hasone end clamped between the housing body 302 a of the housing 302 andthe pressurizing sheet support 302 b and another end clamped between anupper end portion of the holder ring 305 and the chucking plate 306. Thehousing 302, the chucking plate 306, the holder ring 305, and thepressurizing sheet 307 jointly define a pressure chamber 314 in thehousing 302.

An end of a fluid passage 315 such as a pipe is opened to the pressurechamber 314. The fluid passage 315 is connected to a compressed ^(air)source via a selector valve or a regulator, which is not shown. Ends offluid passages 316 and 319 such as pipes are opened to a lower surfaceof the chucking plate 306. The fluid passages 316 and 319 are connectedto the compressed air source via a selector valve or a regulator, whichis not shown. Further, fluid passages 317 and 318 such as pipes areopened to lower surfaces of the elastic pad supports 309 and 313. Thefluid passages 317 and 318 are connected to a vacuum source and thecompressed air source via a selector valve or a regulator, which is notshown.

By depressurizing the lower surfaces of the elastic pad supports 309 and313 via the fluid passage 318, a semiconductor wafer W is attracted toand held on the lower surfaces of the elastic pad supports 309 and 313.While the top ring 301 is rotated, the semiconductor wafer W attractedto and held on the lower surface of the housing 302 is pressed againstthe polishing surface (the upper surface of the polishing pad) 321 onthe rotating polishing table 320. Thus, the semiconductor wafer W ispolished by relative movement between the semiconductor wafer W and thepolishing surface 321. At that time, compressed air is supplied to thepressure chamber 314 and between the lower surface of the chucking plate306 and the semiconductor wafer W via the fluid passages 315, 316, 317,318, and 319. Pressing forces to press the semiconductor wafer W againstthe polishing surface 321 on the polishing table 320 are adjusted byadjustment of pressures.

FIG. 10A is a vertical cross-sectional view showing an attachmentportion of the retainer ring 303 in the top ring 301, and FIG. 10B is aview showing a surface pressure distribution in the retainer ring 303.As shown in FIGS. 10A and 10B, the retainer ring 303 has a first ringmember 331 made of resin and a second ring member 332 made of metal orceramics which has substantially the same plane shape as the first ringmember 331. The first ring member 331 is fastened to a lower surface ofthe second ring member 332 by bolts 333.

An annular groove 332 a is formed in the lower surface of the secondring member 332. The first ring member 331 has an annular projection 331a formed on its upper surface which can fit into the groove 332 a.

Specifically, the retainer ring 303 has an engagement portion to engagethe first ring member 331 and the second ring member 332 with eachother. This arrangement facilitates attachment of the first ring member331 to the second ring member 332 and strengthens fastening of thesemembers. Such an engagement portion may be eliminated. Instead of theengagement portion, a pin may be used to fix the first ring member 331and the second ring member 332 to each other.

Polyetheretherketone (PEEK), polyphenylene sulfide (PPS), full aromaticpolyimide resin, which is refractory plastics, or polycarbonate resincan be used as the resin for the first ring member 331 of the retainerring 303. It is desirable that the first ring member 331, which isbrought into contact with the polishing surface 321, contains particlesserving as abrasive particles when being scraped or particles that causeno damage to a semiconductor wafer. The second ring member 332 is madeof metal such as titanium or stainless, or ceramics such as alumina soas to achieve good heat transfer from the first ring member 331.Preferably, the bolts 333, which fasten the first ring member 331 andthe second ring member 332, may be made of a material having a thermalexpansion coefficient close to that of resin of the first ring member331 or metal (titanium or stainless) or ceramics of the second ringmember 332.

In order to achieve good heat transfer from the first ring member 331 tothe second ring member 332, it is desirable to enlarge a contact area atthe interface. A material having a high thermal expansion coefficientmay preferably be used for the bolts 333. Further, as shown in FIG. 11,a plurality of bolts 333 may be provided at predetermined pitches alonga circumference to fasten the first ring member 331 and the second ringmember 332 to each other. Alternatively, as shown in FIG. 12, aplurality of bolts 333 may be provided at predetermined pitches alongtwo circumferences.

When the top ring 301 including the retainer ring 303 having a structureshown in FIG. 10A is pressed against the polishing surface 321 on thepolishing table 320 under a pressing force F, as shown in FIG. 10B,surface pressures P on the lower surface of the first ring member 331 ofthe retainer ring 303 has a distribution which is slightly small at aninner portion A of the first ring member 331 but is substantiallyuniform from an outer portion to the inner portion.

FIG. 13A is a vertical cross-sectional view showing an attachmentportion of a retainer ring 440 in a conventional top ring 401 to compareoperational effects with the retainer ring 303 having a structure shownin FIG. 10A. FIG. 13B is a view showing a surface pressure distributionin the retainer ring 440. In the example shown in FIG. 13A, the retainerring 440 is formed integrally of resin and fastened and fixed to a lowersurface of a peripheral portion of the housing 302 by bolts.

Since the retainer ring 440 formed integrally of resin is deformed byfastening forces of the bolts attached to the housing 302, it isnecessary to perform a dummy polishing process to remove irregularitieson its surface due to deformation after the retainer ring 440 is newlyattached to the housing 302. Such a dummy polishing process increases adowntime of the apparatus.

Further, when the top ring 401 including the retainer ring 440 having astructure shown in FIG. 13A is pressed against the polishing surface onthe polishing table under a pressing force F, as shown in FIG. 13B,surface pressures P on the lower surface of the retainer ring 440 has adistribution which is substantially uniform from an outer portion to acentral portion of the retainer ring 440 but is greatly varied at theinner portion A.

Here, in order to prevent partial wear of the retainer ring, a ringmember made of stainless (or titanium, ceramics) and a ring member madeof resin may be bonded to each other by an adhesive to form a two-layerstructure. Such a retainer ring having a two-layer structure should bediscarded due to wear of the ring member made of resin. Accordingly,such a retainer ring suffers high cost for expendables and largeenvironmental loads. Further, aged deterioration of the adhesive orseparation due to insufficient adhesion is caused so as to lower thereliability.

In the present embodiment, as shown in FIG. 10A, the retainer ring 303is configured such that the first ring member 331 and the second ringmember 332 are fastened to each other by the bolts 333 to form atwo-layer structure in the vertical direction. Accordingly, it ispossible to achieve high reliability of fastening of the first ringmember 331 and the second ring member 332 and regenerate the retainerring 303 merely by replacement of the worn first ring member 331.Further, the engagement portion is formed by forming the annular groove332 a in the lower surface of the second ring member 332 and forming theannular projection 331 a, which is fitted into the groove 332 a, in theupper surface of the first ring member 331. Accordingly, it is possibleto facilitate assembling the retainer ring 303 and further enhance thereliability of fastening of the first ring member 331 and the secondring member 332. Further, since the retainer ring 303 can be regeneratedmerely by the replacement of the first ring member 331, it is possibleto reduce cost for expendables and environment loads.

Further, the retainer ring 303 is configured such that the first ringmember 331 is fastened to the lower surface of the second ring member332 by the assembly bolts 333. Accordingly, when the retainer ring 303is fastened and fixed to the lower surface of the peripheral portion ofthe housing 302 by the bolts 308 as shown in FIG. 9, the clamp stress ofthe bolts 308 is received by the second ring member 332, which has arigidity higher than the first ring member 331. Thus, the retainer ring303 is prevented from being deformed. Therefore, it is possible toshorten a period of time (downtime) required for a dummy polishingprocess to eliminate irregularities of the surface of the retainer ring303.

In the present embodiment, the first ring member 331 and the second ringmember 332 forming the retainer ring 303 are fastened to each other bythe bolts 333. However, means for fastening the first ring member 331and the second ring member 332 to each other is not limited to thisexample. Various detachable fastening tools may be employed. Forexample, one of the ring members 331 and 332 may have a step portionhaving a small outside diameter, and the other of ring members 332 and331 may have a recess having a large inside diameter. Externallythreaded grooves may be provided in an outer circumferential surface ofthe step portion having a small outside diameter while internallythreaded grooves may be provided in an inner circumferential surface ofthe recess having a large inside diameter. Thus, the first ring member331 and the second ring member 332 may be fastened to each other byscrewing the externally threaded grooves and the internally threadedgrooves on each other. Further, other mechanical fastening tools may beemployed.

When the lower surface of the retainer ring is brought into uniformcontact with the polishing surface, the retainer ring may blockpolishing slurry to be supplied from the exterior of the retainer ringso as to make it difficult to supply polishing slurry sufficiently to aworkpiece to be polished, which is present inside of the retainer ring.Accordingly, slits may be formed in the lower surface of the retainerring to supply polishing slurry therethrough to a workpiece to bepolished, which is present inside of the retainer ring. However, whenslits are formed in a sliding contact surface of the retainer ring,polishing properties vary in a circumferential direction betweenportions having the slits and portions having no slits. A retainer ringaccording to the following embodiments can prevent such drawbacks.

FIG. 14 is a vertical cross-sectional view showing a top ring 510according to a fourth embodiment of the present invention. The top ring510 holds a semiconductor wafer W as a workpiece to be polished, pressthe semiconductor wafer W against the polishing surface on the polishingpad 522, and bring the semiconductor wafer W into sliding contact withthe polishing surface to conduct chemical mechanical polishing.Specifically, the top ring 510 has a retainer ring 512 provided on alower surface of a housing 511 so that a peripheral edge portion of thesemiconductor wafer W is held by an inner circumferential surface of theretainer ring 512. Further, a plate 515 is disposed within the housing511 in a state such that the plate 515 is movable in a verticaldirection via an elastic body ring 514. A pressing force to press thesemiconductor wafer W against the polishing surface is adjusted byadjusting an air pressure of a pressure chamber 513, which is surroundedby the plate 515 and the housing 511. Accordingly, while thesemiconductor wafer W is held and pressed by the top ring 510, it isbrought into sliding contact with the polishing surface of the polishingpad 522 fixed on a polishing table 521. Chemical mechanical polishing isconducted by supplying polishing slurry to the polishing surface.

As shown in FIG. 14, a notch 512 a extending radially inward is formedin an outer circumferential surface of the retainer ring 512. Theretainer ring 512 is formed of, for example, plastic resin. The notch512 a, which has a width of about 0.5 mm to about 1 mm (in a heightdirection of the retainer ring 512), is formed along its perimeter inthe present embodiment. It is desirable that the (radial) depth of thenotch 512 a is set to be about ⅔ of the (radial) width of the retainerring 512. As a matter of course, the width and depth of the notch 512 aare properly determined according to the size, material, and the like ofthe entire retainer ring. Further, it is not necessary to form the notch512 a along its perimeter, and the notch 512 a may partially be formed.

With the notch 512 a extending radially inward on the outercircumferential surface of the retainer ring 512, the rigidity in thevertical direction with respect to the lower surface of the retainerring 512 can gradually be reduced toward its periphery. Thus, an areahaving a low surface pressure is disposed at a peripheral portion of thelower surface of the retainer ring 512. Specifically, a range in whichthe top ring has a low pressing force is provided. Accordingly,polishing slurry can readily be introduced into an inner side of theretainer ring 512. Once the polishing slurry has been introduced intothe inner side of the retainer ring 512, it does not flow out of theretainer ring 512 with ease. Thus, it is possible to increase the amountof polishing slurry supplied to a workpiece held inside of the retainerring 512.

As shown in FIG. 15, it is desirable to fill the notch 512 a with anelastic member 519, such as rubber, by molding or the like. When thenotch 512 a is filled with the elastic member 519, polishing slurry isprevented from being introduced into the notch 512 a and being fixedtherein. Thus, it is possible to prevent troubles due to long-term useof the top ring. Further, since the elastic member 519 such as rubber isfilled, reduction of the rigidity is not inhibited at the peripheralportion of the top ring.

Further, as shown in FIG. 16, the notch 512 a may be formed at aboundary portion of a lower surface of the housing 511 disposed abovethe retainer ring 512. Specifically, a non-contact portion (notch) 512 ais provided outside of a joint portion between the retainer ring 512 andthe housing 511. Accordingly, the rigidity of the retainer ring 512 inthe vertical direction can be reduced toward an outer side of theretainer ring 512. Thus, the surface pressure of the polishing surfaceon the lower surface of the retainer ring 512 can be reduced toward theouter side of the retainer ring 512. As a result, as in the above case,polishing slurry can be prevented from being introduced into an innerside of the retainer ring 512.

An elastic member such as rubber may be filled into the non-contactportion 512 a provided between the lower surface of the housing 511 andthe upper surface of the retainer ring 512 as shown in FIG. 16. In thiscase, as with the elastic member 519 shown in FIG. 15, polishing slurrycan be prevented from being introduced into and fixed to the interior ofthe non-contact portion 512 a.

FIG. 17A shows a portion of a top ring 510 according to a fifthembodiment of the present invention. In this top ring 510, an extendedportion 512 c extending outward is disposed at a bottom portion of acylindrical retainer ring 512. Because the extended portion 512 c isthinner than a thick portion of the retainer ring 512, the extendedportion 512 c can reduce the vertical rigidity with respect to the lowersurface of the retainer ring 512.

FIG. 17B shows a portion of a top ring 510 according to a sixthembodiment of the present invention. The top ring 510 has a notch 512 apositioned right above an extended portion 512 c. With this arrangement,the vertical rigidity of the retainer ring 512 can further be reducedtoward an outer side of the retainer ring 512 as compared to thestructure of the extended portion shown in FIG. 17A.

For example, the extended portion 512 c shown in FIGS. 17A and 17Bpreferably has a thickness of about 1 mm to about 2 mm and a radiallength of about 5 mm. When the notch 512 a is formed as shown in FIG.17B, it is desirable that the extended portion 512 c has a width ofabout 0.5 mm to about 1 mm and a (radial) length that is about ⅔ of a(radial) width of the retainer ring as described above. However, thesedimensions should be properly changed according to the overall dimensionor material of the retainer ring 512. Further, it is not necessary toform the extended portion 512 c and the notch 512 a along the perimeterof the retainer ring 512, and the extended portion 512 c and the notch512 a may partially be provided.

A material used for a portion of the retainer ring 512 which is broughtinto contact with the polishing surface may be different from a materialused for a portion of the retainer ring 512 which is brought intocontact with the housing 511. FIGS. 18A and 18B show examples in whichthe retainer ring 512 is formed of a plurality of materials. Forexample, as shown in FIGS. 18A and 18B, a ring member 512 f which isbrought into contact with the polishing surface 522 may be made of acorrosion-resistant material, whereas a retainer portion 512 d which isbrought into contact with the housing 511 may be made of stainless. Insuch a case, when a notch is formed in an inner circumferential surfaceof a contacting portion between the ring member 512 f and the retainerportion 512 d, the surface pressure can be reduced at an outer side ofthe retainer ring 512.

In this case, as shown in FIG. 18A, an intermediate medium 512 e may beprovided on bonding surfaces between the ring member 512 f and the andthe retainer portion 512 d. Alternatively, as shown in FIG. 18B, thering member 512 f and the retainer portion 512 d may be bonded directlyto each other.

FIG. 19 shows a variation of the retainer ring 512 shown in FIG. 14. Inthis example, a material used for a portion 512 h that is reduced inrigidity is more likely to be scraped than a material used for a portion512 g that is not reduced in rigidity. For example, the portion 512 hthat is reduced in rigidity is made of PPS, and the portion 512 g thatis not reduced in rigidity is made of PEEK. These portions are bonded toeach other. With this arrangement, since the portion 512 h having alower rigidity produces a reduced pressure, a removal rate of theretainer ring 512 becomes lower than the portion 512 g that is notreduced in rigidity. When the retainer ring 512 is used for a long term,steps caused by differences of removal rates change a surface pressuredistribution of the retainer ring 512. If an initial surface pressuredistribution is changed, the amount of slurry to be supplied to asemiconductor wafer is changed. Accordingly, by using a material that islikely to be scraped for the portion 512 g having a lower rigidity, itis possible to reduce the differences of the amount of removal.

In the embodiment shown in FIG. 14, even if differences of the amount ofremoval are produced, a scraped portion further reduces the rigidity ofa portion that is not scraped. Specifically, by optimizing thepositional height and depth of the notch 512 a, a variation of thesurface pressure can be reduced even if differences of the amount ofremoval are produced in the case of the same material.

In the examples shown in FIGS. 18A and 18B, a portion having a highrigidity is first scraped so that a high surface pressure is applied toa portion that is not scraped. Accordingly, a uniform distribution ofthe amount of removal can be achieved by properly designing the size ofthe notch 512 a.

FIG. 20 is a graph showing a surface pressure distribution in theretainer ring 512 shown in FIG. 17B. For example, in the retainer ring512 shown in FIG. 17B, the surface pressure distribution is highest onan inner surface R₀ of the retainer ring 512. The surface pressuredistribution is lowered on an outer surface R₁ of the retainer ring 512by interaction of the notch 512 a and the extended portion 512 c. Thesurface pressure is further reduced on an outer surface R₂ of theextended portion 512 c.

Accordingly, the semiconductor wafer W to be polished and the lowersurface of the retainer ring 512 are brought into sliding contact withthe polishing surface 522 between the rotating top ring 510 and thepolishing surface 522 on the rotating and/or revolving polishing pad522. Polishing slurry supplied to a central portion of the polishing pad522, which is not shown, or a portion of the polishing pad 522 near aperipheral portion of the retainer ring 512 from a nozzle is introducedbetween the lower surface of the retainer ring 512 and the polishingsurface of the polishing pad 522 from the peripheral portion of theretainer ring 512 which has a low surface pressure. Thus, the polishingslurry can readily be supplied to the interior of the retainer ring 512.Specifically, polishing slurry can be supplied uniformly to the interiorof the retainer ring by provision of a portion having a low surfacepressure along the perimeter of the retainer ring 512. Accordingly,polishing slurry can be supplied uniformly to the entire surface of thesemiconductor wafer W to be polished. Thus, uniform polishing propertiescan be obtained.

When polishing slurry is supplied to an upper surface (polishingsurface) of the polishing pad 522 from a rear face of the polishing pad522 through one or more openings provided in at least portions of thepolishing pad 522 which are brought into contact with the semiconductorwafer W, used polishing slurry can satisfactorily be discharged from thesurface of the semiconductor wafer W toward the peripheral portion ofthe retainer ring 512 by effect of the retainer ring 512 having thenotch 512 a as described above. Accordingly, since new polishing slurryis continuously supplied uniformly to the entire surface of the surfaceof the semiconductor wafer W to be polished, uniform polishingproperties can be obtained. Such a method of supplying polishing slurryis suitable for a revolving polishing pad (having a radius e) or a casein which the top ring 510 passes through a central portion of a rotatingpolishing pad 522.

Further, a slit having a size and a shape such that it does not cancelthe aforementioned surface pressure gradient effect of the retainer ring512 due to the notch 512 a may be provided in a sliding contact surfaceof the retainer ring so as to promote uniform supply of slurry to thesurface to be polished.

According to the embodiments, polishing slurry can readily be supplieduniformly to the interior of a retainer ring, which holds a peripheraledge of a workpiece to be polished. Thus, there can be provided apolishing apparatus which has good polishing properties over the entiresurface of a surface of a workpiece to be polished.

In the above embodiments, the present invention can be applied to anytop ring which holds a peripheral edge portion of a workpiece and bringthe workpiece into sliding contact with a polishing surface. Thus, thepresent invention is not limited to examples in which the top ring isrotated while the polishing table is rotated. For example, the presentinvention can be applied to an example in which the top ring holds aworkpiece to be polished and make a translational orbital movement withrespect to the polishing surface.

The polishing table is employed in the above embodiments. However, thepresent invention is not limited to a polishing apparatus having apolishing table. The present invention can be applied to any polishingapparatus as long as the polishing apparatus holds a workpiece to bepolished by a top ring, presses the workpiece against the polishingsurface, and provides a relative movement between the workpiece and thepolishing surface to polish the workpiece.

Although certain preferred embodiments of the present invention havebeen described above, it should be understood that the present inventionis not limited to the above embodiments. As a matter of course, variouschanges may be made therein without departing from the scope of thepresent invention.

INDUSTRIAL APPLICABILITY

The present invention is suitably used for a polishing apparatus forpolishing a workpiece to be polished, such as a semiconductor wafer, byholding the workpiece and pressing the workpiece against a polishingsurface.

1. A polishing apparatus comprising: a polishing surface; a top ring forholding a workpiece to be polished; and a top ring shaft for pressingsaid top ring against said polishing surface, said top ring including: aretainer ring for holding a peripheral edge portion of the workpiece, ahousing substantially in a form of a disk, said housing being connectedto said top ring shaft, and a sliding contact joint interconnecting saidretainer ring and said housing in a state such that said retainer ringand said housing are brought into sliding contact with each other. 2.The polishing apparatus as recited in claim 1, wherein said slidingcontact joint comprises a free joint to bring said retainer ring andsaid housing into sliding contact with each other.
 3. The polishingapparatus as recited in claim 2, wherein said free joint comprises aball joint.
 4. A polishing apparatus comprising: a polishing surface; atop ring for holding a workpiece to be polished; and a top ring shaftfor pressing said top ring against said polishing surface, said top ringincluding: a retainer ring for holding a peripheral edge portion of theworkpiece, a housing substantially in a form of a disk, said housingbeing connected to said top ring shaft, and a joint interconnecting saidretainer ring and said housing, said joint having a sufficient highrigidity in horizontal and vertical directions and a low flexuralrigidity.
 5. The polishing apparatus as recited in claim 4, wherein saidjoint is disposed outside of a center of a radial width of said retainerring.
 6. The polishing apparatus as recited in claim 4, wherein saidjoint has a cross-section constricted at a vertically central portionthereof.
 7. A polishing apparatus comprising: a polishing surface; a topring for holding a workpiece to be polished; and a top ring shaft forpressing said top ring against said polishing surface, said top ringincluding: a retainer ring for holding a peripheral edge portion of theworkpiece, and a housing substantially in a form of a disk, said housingbeing connected to said top ring shaft, wherein a rigidity of saidhousing is increased so that an inclination of a lower surface of saidretainer ring is reduced with respect to said polishing surface whensaid top ring is pressed against said polishing surface.
 8. A polishingapparatus comprising: a polishing surface; and a top ring for holding aworkpiece to be polished, said top ring including a retainer ring forholding a peripheral edge portion of the workpiece, wherein saidretainer ring includes: a first ring member made of resin; a second ringmember made of metal or ceramic; and a fastening tool for fastening saidfirst ring member and said second ring member in a manner such that saidfirst ring member and said second ring member can be detached as twolayers in a vertical direction.
 9. The polishing apparatus as recited inclaim 8, wherein said first ring member is brought into contact withsaid polishing surface.
 10. The polishing apparatus as recited in claim9, wherein said first ring member includes particles serving as abrasiveparticles when said first ring member is scraped.
 11. The polishingapparatus as recited in claim 8, wherein said retainer ring furtherincludes an engagement portion to fit said first ring member and saidsecond ring member into each other.
 12. The polishing apparatus asrecited in claim 8, wherein said retainer ring is configured such thatsaid retainer ring can be regenerated merely by replacement of saidfirst ring member.
 13. The polishing apparatus as recited in claim 8,where said fastening tool comprises a bolt.
 14. A retainer ring forholding a peripheral edge portion of a workpiece to be polished in a topring for pressing the workpiece against a polishing surface and bringingthe workpiece into sliding contact with the polishing surface, saidretainer ring comprising: a first ring member made of resin; a secondring member made of metal or ceramic; and a fastening tool for fasteningsaid first ring member and said second ring member in a manner such thatsaid first ring member and said second ring member can be detached astwo layers in a vertical direction.